Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations (readOnlyHint=true, idempotentHint=true, destructiveHint=false) already indicate a safe read operation. The description adds valuable context beyond that: it's free, unauthenticated, and billable calls return X-Credits-Charged and X-Credits-Balance headers. This is exactly the kind of extra behavioral detail that helps an agent.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is dense but complete—three sentences, no fluff, and the core purpose is front-loaded. Every sentence adds actionable info (what's returned, cost/authentication, header behavior), and it ends with a clear cost indicator.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no input schema, no output schema, and no parameters, the description carries the entire burden—and it fully delivers. It explains the return payload, the response headers, the access requirements (none), and the cost. An agent can call this tool without any further information.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool has zero parameters, so the baseline is 4. The description thoroughly explains the return structure (credit value, skills, packs, allowances) and the response headers, which is more than sufficient for a parameterless tool.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Returns') and a precise resource ('current price list as structured JSON') and enumerates exactly what's included (credit value, skills with costs and routes, packs, plan allowances). No sibling is about pricing, so it's unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Clearly describes when to use it (to render live costs to integrators, attribute spend for resellers) and notes it's free and unauthenticated, which implies it's safe to call anytime. It doesn't explicitly name alternatives, but no other sibling handles pricing, so the guidance is sufficient.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.